> Dear Community members,>> I often see on this site an at the StackExchange the repeating questions> of how to rearrange some expression, that Mathematica "likes" to keep in> one form, but the user prefers another one. It is like in this trivial> example:>> (x^2 - 1)/(x + 1) // Simplify>> that Mathematica returns -1+x, rather than x-1 that might be wished by th=e> user.>> I have seen many answers to this questions, and gave few mine. The proble=m> here is that the answers are non-universal: they strongly depend upon the> expression in question. Besides, they require some additional programming=,> and the more complex is the formula to sort, the longer will be the part =of> the sorting code.>> It seems that the problem of sorting terms of analytic expressions in the> desired order might be solved, if one could assign tags to the terms to b=e> sorted, and then sort the terms according to a specified list of such tag=s.>> Now comes my question, do you know how to apply tags to expression terms?>> I have seen an analogous functionality in the Presentation Master, the> package of David Park. There, however, the tags are used to be assigned =to> sub expressions, the held part of the expression in question. David, is i=t> possible to assign tags to expressions that are not held?>> Thank you in advance.> Alexei>> Alexei BOULBITCH, Dr., habil.> IEE S.A.> ZAE Weiergewan,> 11, rue Edmond Reuter,> L-5326 Contern, LUXEMBOURG>> Office phone : +352-2454-2566> Office fax: +352-2454-3566> mobile phone: +49 151 52 40 66 44>> e-mail: alexei.boulbitch@iee.lu>>>>>